Vibration-resistant, heat-insulating casting and method of making

ABSTRACT

Ceramics adapted to be enveloped in a casting having a cumulative particle size distribution such that the percentage of particles with sizes of less than 44μ lies within the range of 14.5-50% and the balance consists of particles the maximum size of which ranges from 500-2,000μ, in order to produce vibration-resistant ceramic parts which may be enveloped in a casting.

This application is a continuation of U.S. Application Ser. No. 317,340,filed Nov. 2, 1981, which in turn is a continuation of Application Ser.No. 161,404, filed June 20, 1980, which in turn is a continuation ofU.S. Application Ser. No. 924,348, filed July 13, 1978, which in turn isa continuation of U.S. Application Ser. No. 715,977, filed Aug. 19,1976, which application is a division of Application Ser. No. 559,882,filed Mar. 19, 1975, all now abandoned.

BACKGROUND OF THE INVENTION

Various attempts have been made to produce heat-insulated castings byenveloping ceramic parts in aluminum or cast iron castings. Since themodulus of elasticity of ceramics is considerably higher than that ofmetal and the coefficient of expansion of ceramics is lower than that ofmetal, compressive stress is developed in the ceramics and tensilestress in the metal at the boundary between the ceramic part and themetal as the molten metal solidifies and shrinks during cooling.Consequently, either the ceramic part is crushed or the metal yields orbreaks down under tension. Usually the ceramic part, being weaker thanthe metal, is crushed. To avoid such crushing, the surface of theceramic part which comes into contact with the metal is provided with alayer of a porous substance, which is compressed when the ceramic isenveloped in the casting, thereby preventing the ceramic part from beingcrushed. This method has, however, drawbacks in that when the layer ofporous substance is too thick, the casting-enveloped ceramic part has apoor self-supporting strength and fails when subjected to slightvibration; and when the layer of porous substance is too thin, theceramic part is crushed. In this method, depending on the properties ofthe layer of porous substance or the size and shape of the ceramic part,the appropriate thickness of the layer of porous substance is supposedto be 0.1-0.3 mm for, say, a cylindrical ceramic part about 50 mm indiameter. It is, however, extremely difficult to provide a layer of aporous substance on the ceramic part, with the thickness of the layercontrolled to within such a narrow range.

Another method of producing heat-insulated castings is available,according to which a heat-insulating material is adhesively securedaround a pipe of heat-resistant metal and the pipe is enveloped in acasting. In this case, however, the heat insulation obtained is not sogood, because of substantial heat conduction from the pipe. Moreover, aheat-resistant metal of poor formability increases the cost ofproduction, for it is exceedingly difficult to produce a pipe ofintricate configuration therefrom.

SUMMARY OF THE INVENTION

The present invention relates to ceramics for use in making ceramicparts when anti-vibration heat-insulated castings are to be produced byenveloping the ceramic part in an aluminum casting or in an iron castingfor support.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing the cumulative particle size distribution inthe ceramics employed in the test examples;

FIG. 2 is a sectional view of the casting mold used for envelopmentcasting;

FIG. 3a is an axial sectional view of a heat-insulated casting, i.e., aceramic pipe enveloped in a casting;

FIG. 3b is an end view of the casting shown in FIG. 3a;

FIG. 4 is a diagram showing the cumulative range of particle sizes inthe ceramic according to the invention;

FIG. 5 is a sectional view taken through a cylinder head;

FIG. 6 shows the arrangement of an engine system;

FIG. 7 is a partially cutaway oblique view of a manifold reactor;

FIG. 8 is an axial sectional view taken through a manifold reactor; and

FIG. 9 is a sectional view taken along the line A--A of FIG. 8.

DETAILED DESCRIPTION OF THE INVENTION

This invention relates to ceramics adapted to be enveloped in a casting,and more specifically to ceramic particles having a special sizedistribution, which can be molded and fired into vibration resistantceramic parts.

The present inventors have discovered that, when a ceramic part ismolded from ceramic particles having a special size distribution, aheat-insulated casting with excellent insulating and anti-vibrationcharacteristics which does not break during envelopment casting can beobtained without modifying the structure and composition of the castproduct as heretofore considered necessary.

To be specific, the present invention is directed to ceramics such asalumina (Al₂ O₃), cordierite (2MgO.2Al₂ O₃.5SiO₂), zirconia (ZrO₂),glass ceramic (Li₂ O.Al₂ O₃.SiO₃) having particle sizes ranging from afew μ to 2000μ. To be more specific, it is directed to ceramics forenvelopment casting characterized in that particles of less than 44μ insize account for 14.5-50% of the total, the balance being particleshaving a maximum size ranging from 500-2000μ, as illustrated in theshaded range of cumulative particle size distribution in FIG. 4.

The ceramics according to the invention are such that, with thecumulative particle size distribution as illustrated above, theresulting mixture of various particles with different sizes can absorbthe strain or stress of being enveloped in a casting, and is notrestricted with respect to the form to be given to said casting. Thus,ceramic parts of any intricate configuration or any size can besuccessfully enveloped in castings, thereby permitting many differentapplications of the ceramic products.

For example, they may be used for keeping the exhaust gas passage in anautomotive cylinder head warm, thereby making it possible to oxidizecarbon monoxide or unburned hydrocarbons and turn them into harmlesswater or carbonic acid gas. Alternatively, they may be used for keepingthe exhaust gas at the exhaust gas inlet of a manifold reactor servingas an auto emission purifier warm, thereby raising the temperature inthe combustion chamber of the manifold reactor and improving theefficiency with which the carbon monoxide and unburned hydrocarbons inthe exhaust gas are converted to harmless water or carbonic acid gas.

Next, test examples will be given to illustrate the effect of thepresent invention.

TEST EXAMPLE 1

A pipe was fabricated from ceramic material having a cumulative particlesize distribution as shown in FIG. 1. This pipe was enveloped in analuminum alloy or iron casting and the resulting product was tested forcastability and resistance to vibration. At the same time, certainspecimens of ceramics were prepared and tested for theircharacteristics.

In the following are described the methods of molding and testing theceramic pipes and the results thereof.

(1) Manufacture of ceramic pipe (A) Materials

Ceramic particles of alumina (Al₂ O₃) and cordierite (2MgO.2Al₂O₃.5SiO₂) were employed. As illustrated in FIG. 1 particles having acumulative distribution of 12 different sizes were used. They had beenobtained by sifting the particles to different sizes through a standardsieve (JIS Z 8801) and mixing them.

(B) Molding of ceramic pipe

The ceramic pipe was manufactured by compounding the ceramic particleswith the following resin composition, kneading the product in ahigh-temperature kneader at 170°-190° C. for 1.5 hours, rolling it bymeans of a hot roll at a roll temperature of 130° C. into a sheet,crushing the sheet in a pelletizer and injection-molding the crushedproducts. The crushed products were then screened and particles morethan 2.38 mm in size were again put through the pelletizer.

The resin composition was made of the following:

    ______________________________________                                        Polystyrene (Styron 470 of                                                                       64.3%                                                      Asahi-Dow Chemical)                                                           Diethylphthalate   10.7%                                                      Stearic acid       25%                                                        ______________________________________                                    

The ceramic and resin composition was compounded as follows:

    ______________________________________                                        a. Case of alumina                                                            Alumina                   84%                                                 Resin composition         16%                                                 (Note: The alumina contained 4% talc as a                                     sintering additive. The alumina used                                          was Showa-Denko's R Morandum W and the                                        talc was made of material supplied by                                         Seto Yogyo Genryo.)                                                           b. Case of cordierite                                                         Cordierite                75%                                                 Resin composition         25%                                                 (Note: The cordierite was one produced by                                     Marusu Yugyo.)                                                                ______________________________________                                    

Injection molding was carried out using a horizontal type injectionmolding machine (built by Meiki Seisakusho Ltd.) under the followingconditions:

    ______________________________________                                        Injection pressure                                                                             800-1000 Kg/cm.sup.2                                         Injection temperature                                                                          180° C.                                               Metal mold temperature                                                                          25° C.                                               Gate             fan gate                                                     ______________________________________                                    

Allowing for shrinkage in the firing of the ceramics, the dimensions ofthe metal mold were set 5% smaller as to the inner diameter and 5%larger as to the outer diameter than the final dimensions of the pipe aslisted in Table 1.

(C) Degreasing and firing of ceramic pipe

The resulting molded product was deburred, degreased and then fired.

For degreasing, one hour was taken to raise the temperature from theambient temperature to 70° C., and 80 hours was taken to raise it from80° C. to 320° C. at a rate of 3° C./hr., and air was blown into thedegreasing furnace throughout this time.

After degreasing, the alumina pipe was fired at 1350°-1750° C. and thecordierite pipe was fired at 1150°-1350° C. The rate of temperatureincrease was set at 100° C./hr. and the firing time was set at 3 hours.The fired pipes were finished by a diamond grinder to the specifieddimensions. As listed in Table 1, four types of pipes were produced.

(2) Cast-enveloping test

The ceramic pipe 1 produced in this manner was provided with a CO₂ core2 as illustrated in FIG. 2. This assembly was placed in a CO₂ cast mold2'; and by pouring molten metal into the mold 2' the pipe was envelopedin a casting. In FIG. 2, reference numeral 3 indicates the gate, 4 therunner, 5 the parting gate, 6' the mold cavity, and 7 is the vent.

The casting enveloped product was finished to form the article shown inFIGS. 3a and 3b by demolding and machining. Reference numeral 6indicates the cast envelope.

                  TABLE 1                                                         ______________________________________                                         Dimensions of pipe and casting-enveloped pipe                                (see FIG. 3)                                                                  Ceramic pipe (mm)   Cast-enveloped pipe (mm)                                                 out.           out.                                                   in. dia.                                                                              dia.    length dia.  flange                                                                              length                              Symbols                                                                              (a)     (b)     (l)    (c)   dia. (d)                                                                            (L)                                 ______________________________________                                        A      40 mm   50 mm   150 mm 70 mm 90 mm 170 mm                              B      30      50      150    70    90    170                                 C      90      100     150    120   140   170                                 D      80      100     150    120   140   170                                 ______________________________________                                    

(3) Vibration test

Four casting-enveloped products with different dimensions were testedfor anti-vibration performance under the following conditions:

    ______________________________________                                        Frequency of vibration                                                                             90 Hz                                                    Vibrational acceleration                                                                           15G (0.92 mm)                                            (amplitude)          30G (1.84 mm)                                                                 45G (2.76 mm)                                            Testing time         60 min.                                                  Vibrational direction                                                                              direction of                                                                  diameter (L) of                                                               casting-enveloped                                                             product.                                                 ______________________________________                                    

(4) Measurement of ceramic part for bending strength and bulk density

In the same way as in the above production of ceramic pipes, testspecimens, 40 mm long×10 mm wide×5 mm thick, were prepared and measuredfor bending strength and bulk density.

The bending test was performed with the span 30 cm and the loading speed0.5 mm/min.

(5) Test results

Tables 3-17 summarize the results of the above-mentioned tests. Thefollowing symbols are used, the method of indication being the same inTable 23.

    ______________________________________                                        For casting enveloping test                                                   ⊚                                                                        Casting-envelopable                                                 ○  Tiny cracks visible to the naked eye                                          developing in the ceramic pipe                                      Δ   Wide cracks occurring in the ceramic pipe                           X         Ceramic pipe broken                                                 For vibration test                                                            ○  Not broken                                                          Δ   Signs of breaking                                                   X         Ceramics totally broken                                             --        No test                                                             ______________________________________                                    

The left side of the tables refers to the results with an aluminmalloy-enveloped product and the right side to the results with a castiron-enveloped product.

(a) Alumina pipe

The results given in Tables 3-14 indicate that the pipes using ceramicmaterials having cumulative particle size distributions Nos. 4-9 can besatisfactorily enveloped in casting with excellent anti-vibrationcharacteristics.

From the above results it follows that in FIG. 4, showing the particlesize vs. cumulative particle size distribution, the shaded arearepresents good performance.

Numerical values for each point in the shaded area of FIG. 4 are listedin Table 2.

                  TABLE 2                                                         ______________________________________                                                             Cumulative particle                                                Particle size                                                                            size distribution                                        No.       (μ)     (%)                                                      ______________________________________                                        1          44        50                                                       2          74        53                                                       3         105        58                                                       4         177        65                                                       5         297        72                                                       6         420        86                                                       7         500        100                                                      8          44        14.5                                                     9          74        19                                                       10        105        23                                                       11        177        29                                                       12        297        38                                                       13        400        45.5                                                     14        500        49.5                                                     15        707        60.5                                                     16        1000       69                                                       17        2000       100                                                      ______________________________________                                    

(b) Cordierite pipe

Tables 15-17 summarize the results with respect to pipes using materialshaving cumulative particle size distributions No. 3, No. 7 and No. 10.

Since cordierite melts at 1400°-1450° C. and accordingly defiesenvelopment in cast iron, the envelopment test was done only withaluminum alloy.

From the test results listed in Tables 15-17, it is clear that in boththe envelopment test and the vibration test, good results can beobtained only when the material is alumina ceramics.

                                      TABLE 3                                     __________________________________________________________________________    Test results with cumulative particle size                                    Distribution No. 1 (alumina ceramics)                                         Firing temperature                Enveloping                                  and shrinkage      Bulk Bending                                                                            Ceramic                                                                            test results                                                                           Vibration test results             Tests                                                                            Firing tem-                                                                           Linear  density                                                                            strength                                                                           pipe Aluminum                                                                            Cast                                                                             Vibrational acceleration           No.                                                                              perature (°C.)                                                                 shrinkage (%)                                                                         (g/cm.sup.3)                                                                       (Kg/cm.sup.2)                                                                      shape                                                                              alloy iron                                                                             15 G                                                                              30 G                                                                              45 G                       __________________________________________________________________________    1-A                                                                              1350    0       2.40 22.4 A    ⊚                                                                    ⊚                                                                 × ×                                                                   --  --                         1-B                          B    ⊚                                                                    ⊚                                                                 × ×                                                                   --  --                         1-C                          C    ⊚                                                                    ⊚                                                                 × ×                                                                   --  --                         1-D                          D    ⊚                                                                    ⊚                                                                 × ×                                                                   --  --                         2-A                                                                              1450    0       2.42 74.6 A    ⊚                                                                    ⊚                                                                 × ×                                                                   --  --                         2-B                          B    ⊚                                                                    ⊚                                                                 × ×                                                                   --  --                         2-C                          C    ⊚                                                                    ⊚                                                                 × ×                                                                   --  --                         2-D                          D    ⊚                                                                    ⊚                                                                 × ×                                                                   --  --                         3-A                                                                              1550    0       2.41 86.7 A    ⊚                                                                    ⊚                                                                 Δ Δ                                                                   × --                                                                        --                         3-B                          B    ⊚                                                                    ⊚                                                                 Δ Δ                                                                   × --                                                                        --                         3-C                          C    ⊚                                                                    ⊚                                                                 Δ ×                                                                   --  --                         3-D                          D    ⊚                                                                    ⊚                                                                 Δ Δ                                                                   --  --                         4-A                                                                              1600    0       2.42 134.6                                                                              A    ⊚                                                                    ⊚                                                                 Δ Δ                                                                   × ×                                                                   --                         4-B                          B    ⊚                                                                    ⊚                                                                 Δ Δ                                                                   × ×                                                                   --                         4-C                          C    ○                                                                            Δ                                                                          Δ ×                                                                   --  --                         4-D                          D    Δ                                                                             Δ                                                                          × ×                                                                   --  --                         __________________________________________________________________________

                                      TABLE 4                                     __________________________________________________________________________    Test results with cumulative particle size                                    Distribution No. 2 (alumina ceramics)                                         Firing temperature                Enveloping                                  and shrinkage      Bulk Bending                                                                            Ceramic                                                                            test results                                                                           Vibration test results             Tests                                                                            Firing tem-                                                                           Linear  density                                                                            strength                                                                           pipe Aluminum                                                                            Cast                                                                             Vibrational acceleration           No.                                                                              perature (°C.)                                                                 shrinkage (%)                                                                         (g/cm.sup.3)                                                                       (Kg/cm.sup.2)                                                                      shape                                                                              alloy iron                                                                             15 G                                                                              30 G                                                                              45 G                       __________________________________________________________________________    5-A                                                                              1350    0       2.45 40.6 A    ⊚                                                                    ⊚                                                                 × ×                                                                   --  --                         5-B                          B    ⊚                                                                    ⊚                                                                 × ×                                                                   --  --                         5-C                          C    ⊚                                                                    ⊚                                                                 × ×                                                                   --  --                         5-D                          D    ⊚                                                                    ⊚                                                                 × ×                                                                   --  --                         6-A                                                                              1450    0       2.44 93.4 A    ⊚                                                                    ⊚                                                                 Δ Δ                                                                   × ×                                                                   --                         6-B                          B    ⊚                                                                    ⊚                                                                 Δ Δ                                                                   × ×                                                                   --                         6-C                          C    ⊚                                                                    ⊚                                                                 Δ Δ                                                                   --  --                         6-D                          D    ⊚                                                                    ⊚                                                                 Δ Δ                                                                   --  --                         7-A                                                                              1550    0       2.46 141.0                                                                              A    ⊚                                                                    ⊚                                                                 ○ ○                                                                 Δ ×                                                                   --                         7-C                          C    ⊚                                                                    ⊚                                                                 ○ ○                                                                 × ×                                                                   --                         7-D                          D    ⊚                                                                    ⊚                                                                 ○ ○                                                                 × ×                                                                   --                         __________________________________________________________________________

                                      TABLE 5                                     __________________________________________________________________________    Test results with cumulative particle size                                    Distribution No. 3 (alumina ceramics)                                         Firing temperature                Enveloping                                  and shrinkage      Bulk Bending                                                                            Ceramic                                                                            test results                                                                           Vibration test results             Tests                                                                            Firing tem-                                                                           Linear  density                                                                            strength                                                                           pipe Aluminum                                                                            Cast                                                                             Vibrational acceleration           No.                                                                              perature (°C.)                                                                 shrinkage (%)                                                                         (g/cm.sup.3)                                                                       (Kg/cm.sup.2)                                                                      shape                                                                              alloy iron                                                                             15 G                                                                              30 G                                                                              45 G                       __________________________________________________________________________    8-A                                                                              1350    0       2.46 52.3 A    ⊚                                                                    ⊚                                                                 × ×                                                                   --  --                         8-B                          B    ⊚                                                                    ⊚                                                                 × ×                                                                   --  --                         8-C                          C    ⊚                                                                    ⊚                                                                 × ×                                                                   --  --                         8-D                          D    ⊚                                                                    ⊚                                                                 × ×                                                                   --  --                         9-A                                                                              1450    0       2.49 118.2                                                                              A    ⊚                                                                    ⊚                                                                 ○ ○                                                                 × ×                                                                   --                         9-B                          B    ⊚                                                                    ⊚                                                                 ○ ○                                                                 × ×                                                                   --                         9-C                          C    ⊚                                                                    ⊚                                                                 ○ ○                                                                 × ×                                                                   --                         10-C                                                                             1550    0       2.47 176.5                                                                              C    ⊚                                                                    ⊚                                                                 ○ ○                                                                 × ×                                                                   --                         10-D                         D    ⊚                                                                    ⊚                                                                 ○ ○                                                                 × ×                                                                   --                         __________________________________________________________________________

                                      TABLE 6                                     __________________________________________________________________________    Test results with cumulative particle size                                    Distribution No. 4 (alumina ceramics)                                         Firing temperature                Enveloping                                  and shrinkage      Bulk Bending                                                                            Ceramic                                                                            test results                                                                           Vibration test results             Tests                                                                            Firing tem-                                                                           Linear  density                                                                            strength                                                                           pipe Aluminum                                                                            Cast                                                                             Vibrational acceleration           No.                                                                              perature (°C.)                                                                 shrinkage (%)                                                                         (g/cm.sup.3)                                                                       (Kg/cm.sup.2)                                                                      shape                                                                              alloy iron                                                                             15 G                                                                              30 G                                                                              45 G                       __________________________________________________________________________    11-A                                                                             1450    0       2.51 130.4                                                                              A    ⊚                                                                    ⊚                                                                 ○ ○                                                                 ○ ○                                                                 Δ Δ            11-B                         B    ⊚                                                                    ⊚                                                                 ○ ○                                                                 ○ ○                                                                 Δ Δ            11-C                         C    ⊚                                                                    ⊚                                                                 ○ ○                                                                 Δ Δ                                                                   --                         11-D                         D    ⊚                                                                    ⊚                                                                 ○ ○                                                                 Δ Δ                                                                   --                         12-A                                                                             1550    0       2.49 181.0                                                                              A    ⊚                                                                    ⊚                                                                 ○  ○                                                                ○ ○                                                                 ○ ○          12-B                         B    ⊚                                                                    ⊚                                                                 ○ ○                                                                 ○ ○                                                                 ○ ○          12-C                         C    ⊚                                                                    ⊚                                                                 ○ ○                                                                 ○ ○                                                                 Δ Δ            12-D                         D    ⊚                                                                    ⊚                                                                 ○ ○                                                                 ○ ○                                                                 Δ Δ            13-A                                                                             1600    0.1     2.53 238.5                                                                              A    ⊚                                                                    ⊚                                                                 ○ ○                                                                 ○ ○                                                                 ○ ○          13-B                         B    ⊚                                                                    ⊚                                                                 ○ ○                                                                 ○ ○                                                                 ○ ○          13-C                         C    ○                                                                            Δ                                                                          ○ ○                                                                 Δ ×                                                                   × --                 13-D                         D    ○                                                                            Δ                                                                          ○ ○                                                                 Δ ×                                                                   --                         __________________________________________________________________________

                                      TABLE 7                                     __________________________________________________________________________    Test results with cumulative particle size                                    Distribution No. 5 (alumina ceramics)                                         Firing temperature                Enveloping                                  and shrinkage      Bulk Bending                                                                            Ceramic                                                                            test results                                                                           Vibration test results             Tests                                                                            Firing tem-                                                                           Linear  density                                                                            strength                                                                           pipe Aluminum                                                                            Cast                                                                             Vibrational acceleration           No.                                                                              perature (°C.)                                                                 shrinkage (%)                                                                         (g/cm.sup.3)                                                                       (Kg/cm.sup.2)                                                                      shape                                                                              alloy iron                                                                             15 G                                                                              30 G                                                                              45 G                       __________________________________________________________________________    14-A                                                                             1450    0       2.94 95.4 A    ⊚                                                                    ⊚                                                                 ○ ○                                                                 ○ ○                                                                 Δ Δ            14-B                         B    ⊚                                                                    ⊚                                                                 ○ ○                                                                 ○ ○                                                                 Δ Δ            14-C                         C    ⊚                                                                    ⊚                                                                 ○ ○                                                                 Δ Δ                                                                   --                         14-D                         D    ⊚                                                                    ⊚                                                                 ○ ○                                                                 Δ Δ                                                                   --                         15-A                                                                             1550    0       2.52 159.4                                                                              A    ⊚                                                                    ⊚                                                                 ○  ○                                                                ○ ○                                                                 ○ ○          15-B                         B    ⊚                                                                    ⊚                                                                 ○ ○                                                                 ○ ○                                                                 ○ ○          15-C                         C    ⊚                                                                    ⊚                                                                 ○ ○                                                                 ○ ○                                                                 Δ Δ            15-D                         D    ⊚                                                                    ⊚                                                                 ○ ○                                                                 ○ ○                                                                 Δ ×            16-A                                                                             1600    0.1     2.55 197.2                                                                              A    ⊚                                                                    ⊚                                                                 ○ ○                                                                 ○ ○                                                                 ○ ○          16-B                         B    ⊚                                                                    ○                                                                         ○ ○                                                                 ○ ○                                                                 Δ ×            16-C                         C    ○                                                                            ○                                                                         ○ ○                                                                 ○ ○                                                                 × ×            16-D                         D    ○                                                                            ○                                                                         ○ ○                                                                 ○ ○                                                                 × ×            __________________________________________________________________________

                                      TABLE 8                                     __________________________________________________________________________    Test results with cumulative particle size                                    Distribution No. 6 (alumina ceramics)                                         Firing temperature                Enveloping                                  and shrinkage      Bulk Bending                                                                            Ceramic                                                                            test results                                                                           Vibration test results             Tests                                                                            Firing tem-                                                                           Linear  density                                                                            strength                                                                           pipe Aluminum                                                                            Cast                                                                             Vibrational acceleration           No.                                                                              perature (°C.)                                                                 shrinkage (%)                                                                         (g/cm.sup.3)                                                                       (Kg/cm.sup.2)                                                                      shape                                                                              alloy iron                                                                             15 G                                                                              30 G                                                                              45 G                       __________________________________________________________________________    17-A                                                                             1350    0       2.52 94.6 A    ⊚                                                                    ⊚                                                                 ○ ○                                                                 Δ Δ                                                                   --                         17-B                         B    ⊚                                                                    ⊚                                                                 ○ ○                                                                 Δ Δ                                                                   --                         17-C                         C    ⊚                                                                    ⊚                                                                 ○ ○                                                                 Δ Δ                                                                   --                         17-D                         D    ⊚                                                                    ⊚                                                                 ○ ○                                                                 Δ Δ                                                                   --                         18-A                                                                             1450    0       2.51 115.2                                                                              A    ⊚                                                                    ⊚                                                                 ○ ○                                                                 ○ ○                                                                 ○ ○          18-B                         B    ⊚                                                                    ⊚                                                                 ○ ○                                                                 ○ ○                                                                 ○ ○          18-C                         C    ⊚                                                                    ⊚                                                                 ○ ○                                                                 ○ ○                                                                 Δ Δ            18-D                         D    ⊚                                                                    ⊚                                                                 ○ ○                                                                 ○ ○                                                                 Δ Δ            19-A                                                                             1550    0       2.53 157.2                                                                              A    ⊚                                                                    ⊚                                                                 ○ ○                                                                 ○ ○                                                                 ○ ○          19-B                         B    ⊚                                                                    ⊚                                                                 ○ ○                                                                 ○ ○                                                                 ○ ○          19-C                         C    ⊚                                                                    ⊚                                                                 ○ ○                                                                 ○ ○                                                                 ○ ○          19-D                         D    ⊚                                                                    ⊚                                                                 ○ ○                                                                 ○ ○                                                                 ○ ○          20-A                                                                             1600    0.2     2.55 195.4                                                                              A    ⊚                                                                    ⊚                                                                 ○ ○                                                                 ○ ○                                                                 ○ ○          20-B                         B    ⊚                                                                    ⊚                                                                 ○ ○                                                                 ○                                                                          ○ ○          20-C                         C    ○                                                                            ○                                                                         ○ ○                                                                 ○ ○                                                                 Δ Δ            20-D                         D    ○                                                                            ○                                                                         ○ ○                                                                 ○ ○                                                                 Δ Δ            __________________________________________________________________________

                                      TABLE 9                                     __________________________________________________________________________    Test results with cumulative particle size                                    Distribution No. 7 (alumina ceramics)                                         Firing temperature                Enveloping                                  and shrinkage      Bulk Bending                                                                            Ceramic                                                                            test results                                                                           Vibration test results             Tests                                                                            Firing tem-                                                                           Linear  density                                                                            strength                                                                           pipe Alumunum                                                                            Cast                                                                             Vibrational acceleration           No.                                                                              perature (°C.)                                                                 shrinkage (%)                                                                         (g/cm.sup.3)                                                                       (Kg/cm.sup.2)                                                                      shape                                                                              alloy iron                                                                             15 G                                                                              30 G                                                                              45 G                       __________________________________________________________________________    21-A                                                                             1350    0       2.51 93.1 A    ⊚                                                                    ⊚                                                                 ○ ○                                                                 ○ ○                                                                 × ×            21-B                         B    ⊚                                                                    ⊚                                                                 ○ ○                                                                 ○ ○                                                                 × ×            21-C                         C    ⊚                                                                    ⊚                                                                 ○ ○                                                                 Δ Δ                                                                   × ×            21-D                         D    ⊚                                                                    ⊚                                                                 ○ ○                                                                 Δ Δ                                                                   × ×            22-A                                                                             1450    0       2.50 153.2                                                                              A    ⊚                                                                    ⊚                                                                 ○ ○                                                                 ○ ○                                                                 ○ ○          22-B                         B    ⊚                                                                    ⊚                                                                 ○ ○                                                                 ○ ○                                                                 ○ ○          22-C                         C    ⊚                                                                    ⊚                                                                 ○ ○                                                                 ○ ○                                                                 ○ ○          22-D                         D    ⊚                                                                    ⊚                                                                 ○ ○                                                                 ○ ○                                                                 ○ ○          23-A                                                                             1550    0       2.53 204.2                                                                              A    ⊚                                                                    ⊚                                                                 ○ ○                                                                 ○ ○                                                                 ○ ○          23-B                         B    ⊚                                                                    ⊚                                                                 ○ ○                                                                 ○ ○                                                                 ○ ○          23-C                         C    ⊚                                                                    ⊚                                                                 ○ ○                                                                 ○ ○                                                                 ○ ○          23-D                         D    ⊚                                                                    ⊚                                                                 ○ ○                                                                 ○ ○                                                                 ○ ○          24-A                                                                             1600    0       2.52 250.0                                                                              A    ⊚                                                                    ⊚                                                                 ○ ○                                                                 ○ ○                                                                 ○ ○          24-B                         B    ⊚                                                                    ⊚                                                                 ○ ○                                                                 ○ ○                                                                 ○ ○          24-C                         C    ⊚                                                                    ⊚                                                                 ○ ○                                                                 ○ ○                                                                 ○ ○          24-D                         D    ⊚                                                                    ○                                                                         ○ ○                                                                 ○ ○                                                                 ○ ○          25-A                                                                             1650    0.2     2.54 364.6                                                                              A    ○                                                                            ○                                                                         ○ ○                                                                 ○ ○                                                                 Δ Δ            25-B                         B    ○                                                                            ○                                                                         ○ ○                                                                 ○ ○                                                                 Δ Δ            25-C                         C    Δ                                                                             Δ                                                                          Δ Δ                                                                   --  --                         25-D                         D    Δ                                                                             Δ                                                                          Δ ×                                                                   --  --                         __________________________________________________________________________

                                      TABLE 10                                    __________________________________________________________________________    Test results with cumulative particle size                                    Distribution No. 8 (alumina ceramics)                                         Firing temperature                Enveloping                                  and shrinkage      Bulk Bending                                                                            Ceramic                                                                            test results                                                                           Vibration test results             Tests                                                                            Firing tem-                                                                           Linear  density                                                                            strength                                                                           pipe Aluminum                                                                            Cast                                                                             Vibrational acceleration           No.                                                                              perature (°C.)                                                                 shrinkage (%)                                                                         (g/cm.sup.3)                                                                       (Kg/cm.sup.2)                                                                      shape                                                                              alloy iron                                                                             15 G                                                                              30 G                                                                              45 G                       __________________________________________________________________________    26-A                                                                             1350    0       2.49 86.2 A    ⊚                                                                    ⊚                                                                 ○ ○                                                                 ○ ○                                                                 × ×            26-B                         B    ⊚                                                                    ⊚                                                                 ○ ○                                                                 ○ ○                                                                 × ×            26-C                         C    ⊚                                                                    ⊚                                                                 ○ ○                                                                 Δ Δ                                                                   --                         26-D                         D    ⊚                                                                    ⊚                                                                 ○ ○                                                                 Δ Δ                                                                   --                         27-A                                                                             1450    0       2.48 138.5                                                                              A    ⊚                                                                    ⊚                                                                 ○ ○                                                                 ○ ○                                                                 ○ ○          27-B                         B    ⊚                                                                    ⊚                                                                 ○ ○                                                                 ○ ○                                                                 ○ ○          27-C                         C    ⊚                                                                    ⊚                                                                 ○ ○                                                                 ○ ○                                                                 ○ ○          27-D                         D    ⊚                                                                    ⊚                                                                 ○ ○                                                                 ○ ○                                                                 ○ ○          28-A                                                                             1550    0       2.50 166.5                                                                              A    ⊚                                                                    ⊚                                                                 ○ ○                                                                 ○ ○                                                                 ○ ○          28-B                         B    ⊚                                                                    ⊚                                                                 ○ ○                                                                 ○ ○                                                                 ○ ○          28-C                         C    ⊚                                                                    ⊚                                                                 ○ ○                                                                 ○ ○                                                                 ○ ○          28-D                         D    ⊚                                                                    ⊚                                                                 ○ ○                                                                 ○ ○                                                                 ○ ○          29-A                                                                             1600    0       2.51 193.1                                                                              A    ⊚                                                                    ⊚                                                                 ○ ○                                                                 ○ ○                                                                 ○ ○          29-B                         B    ⊚                                                                    ⊚                                                                 ○  ○                                                                ○ ○                                                                 ○ ○          29-C                         C    ⊚                                                                    ⊚                                                                 ○ ○                                                                 ○ ○                                                                 ○ ○          29-D                         D    ○                                                                            ○                                                                         ○ ○                                                                 ○ ○                                                                 ○ ○          30-A                                                                             1650    0.3     2.54 271.3                                                                              A    ○                                                                            ○                                                                         ○ ○                                                                 ○ ○                                                                 Δ Δ            30-B                         B    ○                                                                            ○                                                                         ○ ○                                                                 Δ Δ                                                                   Δ Δ            30-C                         C    Δ                                                                             Δ                                                                          × ×                                                                   --  --                         30-D                         D    ×                                                                             ×                                                                          --  --  --                         __________________________________________________________________________

                                      TABLE 11                                    __________________________________________________________________________    Test results with cumulative particle size                                    Distribution No. 9 (alumina ceramics)                                         Firing temperature                Enveloping                                  and shrinkage      Bulk Bending                                                                            Ceramic                                                                            test results                                                                           Vibration test results             Tests                                                                            Firing tem-                                                                           Linear  density                                                                            strength                                                                           pipe Aluminum                                                                            Cast                                                                             Vibrational acceleration           No.                                                                              perature (°C.)                                                                 shrinkage (%)                                                                         (g/cm.sup.3)                                                                       (Kg/cm.sup.2)                                                                      shape                                                                              alloy iron                                                                             15 G                                                                              30 G                                                                              45 G                       __________________________________________________________________________    31-A                                                                             1350    0       2.55 67.3 A    ⊚                                                                    ⊚                                                                 ○ ○                                                                 ○ ○                                                                 × ×            31-B                         B    ⊚                                                                    ⊚                                                                 ○ ○                                                                 ○ ○                                                                 × ×            31-C                         C    ⊚                                                                    ⊚                                                                 ○ ○                                                                 Δ Δ                                                                   --                         31-D                         D    ⊚                                                                    ⊚                                                                 ○ ○                                                                 Δ Δ                                                                   --                         32-A                                                                             1450    0       2.58 135.5                                                                              A    ⊚                                                                    ⊚                                                                 ○ ○                                                                 ○ ○                                                                 ○ ○          32-B                         B    ⊚                                                                    ⊚                                                                 ○ ○                                                                 ○ ○                                                                 ○ ○          32-C                         C    ⊚                                                                    ⊚                                                                 ○ ○                                                                 ○ ○                                                                 ○ ○          32-D                         D    ⊚                                                                    ⊚                                                                 ○ ○                                                                 ○ ○                                                                 ○ ○          33-A                                                                             1550    0       2.59 171.3                                                                              A    ⊚                                                                    ⊚                                                                 ○ ○                                                                 ○ ○                                                                 ○ ○          33-B                         B    ○                                                                            ○                                                                         ○ ○                                                                 ○ ○                                                                 ○ ○          33-C                         C    ○                                                                            ○                                                                         ○ ○                                                                 ○ ○                                                                 Δ Δ            33-D                         D    ○                                                                            ○                                                                         ○ ○                                                                 ○ ○                                                                 Δ Δ            34-A                                                                             1600    0.4     2.60 240.0                                                                              A    ○                                                                            ○                                                                         ○ ○                                                                 ○ ○                                                                 ○ Δ           __________________________________________________________________________

                                      TABLE 12                                    __________________________________________________________________________    Test results with cumulative particle size                                    Distribution No. 10 (alumina ceramics)                                        Firing temperature                Enveloping                                  and shrinkage      Bulk Bending                                                                            Ceramic                                                                            test results                                                                           Vibration test results             Tests                                                                            Firing tem-                                                                           Linear  density                                                                            strength                                                                           pipe Alumina                                                                             Cast                                                                             Vibrational acceleration           No.                                                                              perature (°C.)                                                                 shrinkage (%)                                                                         (g/cm.sup.3)                                                                       (Kg/cm.sup.2)                                                                      shape                                                                              alloy iron                                                                             15 G                                                                              30 G                                                                              45 G                       __________________________________________________________________________    35-A                                                                             1450    0       2.59 77.5 A    ⊚                                                                    ⊚                                                                 ○ ○                                                                 --  --                         35-B                         B    ⊚                                                                    ⊚                                                                 ○ ○                                                                 --  --                         35-C                         C    ○                                                                            ○                                                                         ○ ○                                                                 --  --                         35-D                         D    ○                                                                            ○                                                                         Δ Δ                                                                   --  --                         36-A                                                                             1550    0.4     2.60 122.0                                                                              A    Δ                                                                             Δ                                                                          × ×                                                                   --  --                         36-B                         B    Δ                                                                             Δ                                                                          × ×                                                                   --  --                         36-C                         C    ×                                                                             ×                                                                          --  --  --                         36-D                         D    ×                                                                             ×                                                                          --  --  --                         37-A                                                                             1600    0.7     2.63 201.4                                                                              A    ×                                                                             ×                                                                          --  --  --                         37-B                         B    ×                                                                             ×                                                                          --  --  --                         37-C                         C    ×                                                                             ×                                                                          --  --  --                         37-D                         D    ×                                                                             ×                                                                          --  --  --                         __________________________________________________________________________

                                      TABLE 13                                    __________________________________________________________________________    Test results with cumulative particle size                                    Distribution No. 11 (alumina ceramics)                                        Firing temperature                Enveloping                                  and shrinkage      Bulk Bending                                                                            Ceramic                                                                            test results                                                                           Vibration test results             Tests                                                                            Firing tem-                                                                           Linear  density                                                                            strength                                                                           pipe Aluminum                                                                            Cast                                                                             Vibrational acceleration           No.                                                                              perature (°C.)                                                                 shrinkage (%)                                                                         (g/cm.sup.3)                                                                       (Kg/cm.sup.2)                                                                      shape                                                                              alloy iron                                                                             15 G                                                                              30 G                                                                              45 G                       __________________________________________________________________________    38-A                                                                             1350    0       2.64 40.1 A    ○                                                                            ○                                                                         Δ Δ                                                                   --  --                         38-B                         B    ○                                                                            ○                                                                         Δ Δ                                                                   --  --                         38-C                         C    Δ                                                                             Δ                                                                          --  --  --                         38-D                         D    Δ                                                                             Δ                                                                          --  --  --                         39-A                                                                             1450    0       2.66 88.0 A    ×                                                                             ×                                                                          --  --  --                         39-B                         B    ×                                                                             ×                                                                          --  --  --                         39-C                         C    ×                                                                             ×                                                                          --  --  --                         39-D                         D    ×                                                                             ×                                                                          --  --  --                         40-A                                                                             1550    0.2     2.69 179.3                                                                              A    ×                                                                             ×                                                                          --  --  --                         40-B                         B    ×                                                                             ×                                                                          --  --  --                         40-C                         C    ×                                                                             ×                                                                          --  --  --                         40-D                         D    ×                                                                             ×                                                                          --  --  --                         __________________________________________________________________________

                                      TABLE 14                                    __________________________________________________________________________    Test results with cumulative particle size                                    Distribution No. 12 (alumina ceramics)                                        Firing temperature                Enveloping                                  and shrinkage      Bulk Bending                                                                            Ceramic                                                                            test results                                                                           Vibration test results             Tests                                                                            Firing tem-                                                                           Linear  density                                                                            strength                                                                           pipe Aluminum                                                                            Cast                                                                             Vibrational acceleration           No.                                                                              perature (°C.)                                                                 shrinkage (%)                                                                         (g/cm.sup.3)                                                                       (Kg/cm.sup.2)                                                                      shape                                                                              alloy iron                                                                             15 G                                                                              30 G                                                                              45 G                       __________________________________________________________________________    41-A                                                                             1350    0       2.70 53.9 A    Δ                                                                             Δ                                                                          --  --  --                         41-B                         B    Δ                                                                             Δ                                                                          --  --  --                         41-C                         C    ×                                                                             ×                                                                          --  --  --                         41-D                         D    ×                                                                             ×                                                                          --  --  --                         42-A                                                                             1450    0       2.69 103.6                                                                              A    ×                                                                             ×                                                                          --  --  --                         42-B                         B    ×                                                                             ×                                                                          --  --  --                         42-C                         C    ×                                                                             ×                                                                          --  --  --                         42-D                         D    ×                                                                             ×                                                                          --  --  --                         43-A                                                                             1550    0.2     2.71 161.2                                                                              A    ×                                                                             ×                                                                          --  --  --                         43-B                         B    ×                                                                             ×                                                                          --  --  --                         43-C                         C    ×                                                                             ×                                                                          --  --  --                         43-D                         D    ×                                                                             ×                                                                          --  --  --                         __________________________________________________________________________

                                      TABLE 15                                    __________________________________________________________________________    Test results with cumulative particle size                                    Distribution No. 3 (cordierite ceramics)                                      Firing temperature                                                            and shrinkage      Bulk Bending                                                                            Ceramic                                                                            Enveloping                                                                             Vibration test results             Tests                                                                            Firing tem-                                                                           Linear  density                                                                            strength                                                                           pipe  test results                                                                          Vibrational acceleration           No.                                                                              perature (°C.)                                                                 shrinkage (%)                                                                         (g/cm.sup.3)                                                                       (Kg/cm.sup.2)                                                                      shape                                                                              Aluminum alloy                                                                         15 G                                                                              30 G                                                                              45 G                       __________________________________________________________________________    44-A                                                                             1150    0       1.66 39.9 A    ⊚                                                                       ○                                                                          ×                                                                           --                         44-B                         B    ⊚                                                                       ○                                                                          ×                                                                           --                         44-C                         C    ⊚                                                                       ○                                                                          ×                                                                           --                         44-D                         D    ⊚                                                                       ○                                                                          ×                                                                           --                         45-A                                                                             1200    0.3     1.72 88.8 A    ⊚                                                                       ○                                                                          ×                                                                           --                         45-B                         B    ⊚                                                                       ○                                                                          ×                                                                           --                         45-C                         C    ⊚                                                                       ○                                                                          ×                                                                           --                         45-D                         D    ○ ○                                                                          ×                                                                           --                         46-A                                                                             1250    0.8     1.78 192.4                                                                              A    ○ ○                                                                          ×                                                                           --                         46-B                         B    ○ ○                                                                          ×                                                                           --                         __________________________________________________________________________

                                      TABLE 16                                    __________________________________________________________________________    Test results with cumulative particle size                                    Distribution No. 7 (cordierite ceramics)                                      Firing temperature                                                            and shrinkage      Bulk Bending                                                                            Ceramic                                                                            Enveloping                                                                             Vibration test results             Tests                                                                            Firing tem-                                                                           Linear  density                                                                            strength                                                                           pipe  test results                                                                          Vibrational acceleration           No.                                                                              perature (°C.)                                                                 shrinkage (%)                                                                         (g/cm.sup.3)                                                                       (Kg/cm.sup.2)                                                                      shape                                                                              Aluminum alloy                                                                         15 G                                                                              30 G                                                                              45 G                       __________________________________________________________________________    47-A                                                                             1100    0       1.72 47.8 A    ⊚                                                                       ○                                                                          ○                                                                          ×                    47-B                         B    ⊚                                                                       ○                                                                          ○                                                                          ×                    47-C                         C    ⊚                                                                       ○                                                                          Δ                                                                           ×                    47-D                         D    ⊚                                                                       ○                                                                          Δ                                                                           ×                    48-A                                                                             1150    0       1.70 93.4 A    ⊚                                                                       ○                                                                          ○                                                                          ○                   48-B                         B    ⊚                                                                       ○                                                                          ○                                                                          ○                   48-C                         C    ⊚                                                                       ○                                                                          ○                                                                          ○                   48-D                         D    ⊚                                                                       ○                                                                          ○                                                                          ○                   49-A                                                                             1200    0.1     1.73 155.6                                                                              A    ⊚                                                                       ○                                                                          ○                                                                          ○                   49-B                         B    ⊚                                                                       ○                                                                          ○                                                                          ○                   49-C                         C    ⊚                                                                       ○                                                                          ○                                                                          ○                   49-D                         D    ⊚                                                                       ○                                                                          ○                                                                          ○                   50-A                                                                             1250    0.5     1.78 265.8                                                                              A    ⊚                                                                       ○                                                                          ○                                                                          ○                   50-B                         B    ⊚                                                                       ○                                                                          ○                                                                          ○                   50-C                         C    ⊚                                                                       ○                                                                          ○                                                                          ○                   50-D                         D    ⊚                                                                       ○                                                                          ○                                                                          ○                   51-A                                                                             1300    1.4     1.82 373,6                                                                              A    ○ ○                                                                          ○                                                                          ○                   51-B                         B    ○ ○                                                                          ○                                                                          ○                   51-C                         C    ○ ○                                                                          Δ                                                                           ×                    __________________________________________________________________________

                                      TABLE 17                                    __________________________________________________________________________    Test results with cumulative particle size                                    Distribution No. 10 (cordierite ceramics)                                     Firing temperature                                                            and shrinkage      Bulk Bending                                                                            Ceramic                                                                            Enveloping                                                                             Vibration test results             Tests                                                                            Firing tem-                                                                           Linear  density                                                                            strength                                                                           pipe  test results                                                                          Vibrational acceleration           No.                                                                              perature (°C.)                                                                 shrinkage (%)                                                                         (g/cm.sup.3)                                                                       (Kg/cm.sup.2)                                                                      shape                                                                              Aluminum alloy                                                                         15 G                                                                              30 G                                                                              45 G                       __________________________________________________________________________    52-A                                                                             1100    0       1.82 41.7 A    ⊚                                                                       ○                                                                          ×                                                                           --                         52-B                         B    ⊚                                                                       ○                                                                          ×                                                                           --                         52-C                         C    ⊚                                                                       ○                                                                          ×                                                                           --                         52-D                         D    ⊚                                                                       ○                                                                          ×                                                                           --                         53-A                                                                             1150    0       1.85 62.4 A    ⊚                                                                       ○                                                                          ×                                                                           --                         53-B                         B    ⊚                                                                       ○                                                                          ×                                                                           --                         __________________________________________________________________________

The following are examples of practical uses for heat-insulated castingsproduced by envelopment of the invented ceramic parts.

EXAMPLE 1

A ceramic pipe using the ceramic material of the present invention wascast into the cylinder head of auto engine and submitted to an endurnacetest on the engine stand.

The cylinder head was constructed as shown in FIG. 5, in which 8 is thecasting of the cylinder head (aluminum alloy or cast iron), 9 is thejacket for circulating the cooling water, 10 is the exhaust pipe, 11 isthe valve seat, 12 is the air pipe, 13 is the ceramic pipe according tothe present invention, 14 is the combustion chamber of the engine, and15 is the flange for attaching the exhaust manifold.

In FIG. 5, the exhaust gas from the combustion chamber 14 of the engineis discharged through the exhaust port 16 fitted with the ceramic pipe13 when the exhaust valve 10 opens. In the exhaust port 16, the airintroduced through the air intake pipe 12 is mixed with the exhaust gas,so that the carbon monoxide and hydrocarbons in the exhaust gas aretransformed into harmless carbonic acid gas and water. The gas purifiedin the exhaust port 16 passes out through the opening 16' into themanifold reactor (not shown). The purifying performance will bedescribed in Examples 2 and 3. In the present example the vibrationresisting properties and durability are described.

Table 18 gives the conditions of the endurance test and Table 19summarizes the test results.

                  TABLE 18                                                        ______________________________________                                        Items       Conditions                                                        ______________________________________                                        Displacement                                                                              Internal combustion engine mounted with                                       aluminum cylinder head                                                        1600 cc                                                                       Internal combustion engine mounted with                                       cast iron cylinder head                                                       2000 cc                                                           Gasoline    Regular gasoline                                                  Dynamo      D-C dynamo                                                        Test procedure                                                                            Hot-cold test with 10 min of firing and                                       5 min of motoring at 5500 rpm                                     Test time   100 hours                                                         Secondary   ˜80 cc/engine revolutions                                   air volume                                                                    ______________________________________                                    

                  TABLE 19                                                        ______________________________________                                        Test results                                                                                    Test results                                                Test No. Ceramic pipe   Engine A Engine B                                     ______________________________________                                        1        Test No. 10-A  X        X                                            2        Test No. 15-A  ○ ○                                     3        Test No. 19-A  ○ ○                                     4        Test No. 28-A  ○ ○                                     5        Test No. 33-A  ○ ○                                     6        Test No. 35-A  X        X                                            7        Test No. 45-A  X        X                                            8        Test No. 48-A  ○ ○                                     9        Test No. 49-A  ○ ○                                     10       Test No. 53-A  X        X                                            ______________________________________                                         Note                                                                          1 Test No. indicated in the column of ceramic pipe means that with respec     to the material quality, wall thickness and shape, the pipe is the same a     the one bearing the same number in Tables 3-17; with respect to dimension     it is nearly the same as the one bearing the symbol A in Table 1.             2 Engine A is one equipped with an aluminum alloy cylinder head and Engin     B is one equipped with a cast iron cylinder head.                             3 In the test results the mark ○ means nothing wrong and X means a     broken ceramic pipe.                                                     

Comparing the results between Table 19 and Tables 3-17, it is seen thatthey correspond well. In short, the pipe that permits envelopment by acasting and can stand a vibrational acceleration of about 45 G is foundto be capable of withstanding the endurance test on the engine stand.

EXAMPLE 2

The results of tests comparing the gas purification when a cylinder headwith a casting-enveloped ceramic pipe is used and when one with aceramic pipe which is not enveloped by a casting is used as mentioned inExample 1 will now be described.

Table 20 gives the test conditions and Table 21 summarizes the testresults.

The results are indicated with the exhaust volume of CO, HC and NO_(x)from the engine using a conventional cylinder head taken as 100.

                  TABLE 20                                                        ______________________________________                                        Test conditions                                                               Engine running Engine revolution                                                                          Time                                              conditions     (rpm)        (min.)                                            ______________________________________                                        Start          0                                                              ↓       ↓                                                       Idle           850          2                                                 ↓       ↓     ↓                                          Accelerate     2000         3                                                 ↓       ↓     ↓                                          Accelerate     4000         5                                                 ↓       ↓     ↓                                          Decelerate     2000         3                                                 ↓       ↓                                                       Stop           0                                                              ______________________________________                                    

                  TABLE 21                                                        ______________________________________                                        Exhaust gas purifying performance                                             Engine                                                                        revolution components of exhaust gas                                          (rpm)      CO (%)      HC (%)   NO.sub.x (%)                                  ______________________________________                                        Ceramic pipe-                                                                             82          23      100                                           fitted engine                                                                 Conventional                                                                             100         100      100                                           engine                                                                        ______________________________________                                    

As evident from the results given in Table 21, the effect in eliminatingNO_(x) is not significant, but the effect in eliminating HC is great andsome CO as well can be removed.

In this test the air intake through the air pipe 12 was set at 80 cc perrevolution of the engine and a ceramic pipe with the same material andwall thickness as the one in Test No. 28 and a shape similar to the oneof symbol A was tested.

EXAMPLE 3

In Example 2 the exhaust gas purifying performance of a cylinder headwith a casting-enveloped ceramic pipe was described. In Example 3, theexhaust gas purifying performance when a manifold reactor having abuilt-in ceramic pipe according to the present invention was connectedto this cylinder head will be described.

The manifold reactor 17 is fitted into the engine system in anarrangement such as that illustrated in FIG. 6, in which referencenumeral 18 indicates the engine, 19 the exhaust pipe, 20 the sub-mufflerand 21 the main muffler.

The structure of the manifold reactor is illustrated in FIG. 7, which isa partially cutaway oblique view of the reactor as attached to theengine 18. FIG. 8 is a sectional view thereof and FIG. 9 is a view takenalong the A--A line in FIG. 8.

In FIGS. 7 and 8, 22 indicates the combustion chamber, 23 the ceramicpipe, 24 the outer casing, 25 the port liner to convey the exhaust gasfrom the cylinder head to the manifold reactor, and 26 the exhaust portliner to guide the reburnt gas to the exhaust pipe 19, for discharge.

As explained in Example 1, the exhaust gas burned in the combustionchamber 14 of the engine goes to the exhaust port 16, where it mixeswith the air taken in via the air pipe 12, and the mixture is introducedthrough the port liner 25 into the combustion chamber 22 of the manifoldreactor. In this chamber 22 the reburnable components (CO and HC) in theexhaust gas are reburnt and transformed into harmless CO₂ and H₂ O. Theexhaust gas is desirably kept as hot as possible and for this reason thepart through which the exhaust gas passes is heat-insulated with aceramic pipe.

In this example, the exhaust port 16 of the cylinder head 8 isheat-insulated by the ceramic pipe 13, while the combustion chamber 22of the manifold reactor is heat-insulated by the ceramic pipe 23. Bothends of the ceramic pipe 23 for the manifold reactor are heat-insulatedby a ceramic fiber sheet 29 sandwiched between the heat-resistant metalplate 27 and the end plate 28.

In this example, the ceramic pipe 13 for the cylinder head 8 wasenveloped by a casting of aluminum alloy, JIS-AC8N, while the ceramicpipe 23 for the outer casing 24 of the manifold reactor 18 was envelopedby a casting of iron, JIS-FCG-23. The ceramic pipe 13 for the cylinderhead is the same in material and wall thickness as and similar in shapeto, the one used in Test No. 23-A of Table 8, while the ceramic pipe 23for the manifold reactor is the same in material and wall thickness as,and similar in shape to, the one used in Test No. 22-C of Table 8.

An engine equipped with the above cylinder head and manifold reactor wassubjected to an endurance test under the test conditions as listed inTable 18.

After testing, the exhaust port of the cylinder head was cut at fourspots but examination revealed nothing wrong with the ceramic pipe 13.The manifold reactor was also cut and examined as shown in FIG. 8, butnothing wrong was revealed with the ceramic pipe 23.

Next the elimination of the harmful components (CO, HC, NO_(x))exhausted from the system composed as above was checked by testing underthe conditions listed in Table 20. The results are summarized in Table22, in which the numerical values are indicated, taking as 100 thevolume of the harmful components exhausted from a conventional enginesystem.

The results in Table 22 testify to the effectiveness of the system inthis example.

                  TABLE 22                                                        ______________________________________                                         Exhaust gas purifying performance                                                       Components of exhaust gas                                          Engine type  CO (%)      HC (%)   NO.sub.x (%)                                ______________________________________                                        System of the                                                                              15.4        12.3     100                                         present invention                                                             Conventional system                                                                        100         100      100                                         ______________________________________                                    

EXAMPLE 4

A slurry was made by adding to ceramic (alumina) particles havingcumulative particle size distribution No. 7 a 25% aqueous solution ofpolyvinylalcohol (PVA) in the amount of 15.5%. The slurry was pouredinto a gypsum mold to form ceramic pipes, which were dried at 100° C.for 5 hours, followed by firing at different temperatures. Using thesepipes, casting-enveloping tests and vibration tests of the cast productswere carried out. At the same time, using test specimens similar to theones used in the preceding example, the bending strength was measured,the results being summarized in Table 23.

The results of Table 23 are approximately the same as those of Table 8for the last example. They show that there is no difference between theperformance of the ceramics according to Example 4 and that of aninjection-molded product using a resin composition, so that theperformance of the ceramics according to the present invention issatisfactory regardless of the molding process.

                                      TABLE 23                                    __________________________________________________________________________    Test results with cumulative particle size                                    Distribution No. 7 (alumina ceramics, slurry-casting)                         Firing temperature                Enveloping                                  and shrinkage      Bulk Bending                                                                            Ceramic                                                                            test results                                                                           Vibration test results             Tests                                                                            Firing tem-                                                                           Linear  density                                                                            strength                                                                           pipe Aluminum                                                                            Cast                                                                             Vibrational acceleration           No.                                                                              perature (°C.)                                                                 shrinkage (%)                                                                         (g/cm.sup.3)                                                                       (Kg/cm.sup.2)                                                                      shape                                                                              alloy iron                                                                             15 G                                                                              30 G                                                                              45 G                       __________________________________________________________________________    54-A                                                                             1350    0       2.51 101.2                                                                              A    ⊚                                                                    ⊚                                                                 ○ ○                                                                 ○ ○                                                                 --                         54-B                         B    ⊚                                                                    ⊚                                                                 ○ ○                                                                 ○ ○                                                                 --                         54-C                         C    ⊚                                                                    ⊚                                                                 ○ ○                                                                 Δ Δ                                                                   --                         54-D                         D    ⊚                                                                    ⊚                                                                 ○ ○                                                                 Δ ×                                                                   --                         55-A                                                                             1450    0       2.51 167.2                                                                              A    ⊚                                                                    ⊚                                                                 ○ ○                                                                 ○ ○                                                                 ○ ○          55-B                         B    ⊚                                                                    ⊚                                                                 ○ ○                                                                 ○ ○                                                                 ○ ○          55-C                         C    ⊚                                                                    ⊚                                                                 ○ ○                                                                 ○ ○                                                                 ○ ○          55-D                         D    ⊚                                                                    ⊚                                                                 ○ ○                                                                 ○ ○                                                                 ○ ○          56-A                                                                             1550    0       2.53 214.3                                                                              A    ⊚                                                                    ⊚                                                                 ○ ○                                                                 ○ ○                                                                 ○ ○          56-B                         B    ⊚                                                                    ⊚                                                                 ○ ○                                                                 ○ ○                                                                 ○ ○          56-C                         C    ⊚                                                                    ⊚                                                                 ○ ○                                                                 ○ ○                                                                 ○ ○          56-D                         D    ⊚                                                                    ⊚                                                                 ○ ○                                                                 ○ ○                                                                 ○ ○          57-A                                                                             1600    0       2.52 262.8                                                                              A    ⊚                                                                    ⊚                                                                 ○ ○                                                                 ○ ○                                                                 ○ ○          57-B                         B    ⊚                                                                    ⊚                                                                 ○ ○                                                                 ○                                                                          ○ ○          57-C                         C    ⊚                                                                    ⊚                                                                 ○ ○                                                                 ○ ○                                                                 ○ ○          57-D                         D    ⊚                                                                    ⊚                                                                 ○ ○                                                                 ○ ○                                                                 ○ ○          __________________________________________________________________________

As described above, it is possible to obtain a ceramic pipe which may beenveloped in a casting of aluminum alloy or cast iron when the ceramicsof the present invention are employed. The heat-insulated casting, i.e.,the enveloped ceramic pipe according to the present invention has themerits of being highly effective in purifying the exhaust gas from autoengines and having excellent resistance to vibration.

In the conventional practice of heat-insulating a manifold reactor, afibrous heat-insulating material was sandwiched in a heat-resistantmetal cylinder, but when the ceramic pipe of the present invention isadopted, the structure can be simplified and the cost can be lowered. Ina conventional heat-resistant metal cylinder which contains severalwelded spots, repetition of the cooling and heating cycle causescracking of such spots and the fibrous heat-insulating material isliable to fly out through cracks into the exhaust gas. This difficultyis eliminated when the ceramics of the present invention are employed.

Moreover, the ceramics of the present invention may be used for bothinjection-molding and slurry-casting. Thus it is suitable for the massproduction of intricate configurations and involves no difficulty inmanufacture.

What is claimed is:
 1. A vibration-resistant heat-insulating castingconsisting essentially of (a) a ceramic part manufactured by moldingparticles of ceramic material having a cumulative particle sizedistribution within the shaded area indicated in FIG. 4 of the drawingsas filed, and firing the molded ceramic, and (b) a metal cast aroundsaid ceramic part, said ceramic material being selected from the groupconsisting of alumina, cordierite, zirconia and glass ceramic and saidcasting metal being selected from aluminum alloy and cast iron.
 2. Thecasting of claim 1, wherein said ceramic material is selected fromalumina and cordierite.
 3. The casting of claim 1, wherein said castingis in the form of a pipe.
 4. A vibration-resistant heat-insulatingcasting consisting essentially of (a) a ceramic part manufactured bymolding particles of ceramic material having a cumulative particle sizedistribution such that 14.5-50% of the particles are less than 44μ insize while the balance consists essentially of particles having amaximum particle size ranging between 500 and 2000μ, and firing themolded ceramic, and (b) a metal cast around said ceramic part, saidceramic material being one selected from the group consisting ofalumina, cordierite, zirconia and glass ceramic and said casting metalbeing selected from aluminum alloy and cast iron.
 5. The casting ofclaim 4, wherein said ceramic material is one selected from alumina andcordierite.
 6. The casting of claim 4, wherein said casting is in theform of a pipe.
 7. A vibration-resistant heat-insulating castingconsisting essentially of (a) a ceramic part manufactured by moldingparticles of ceramic material having a cumulative particle sizedistribution such that 14.5-50% of the particles are less than 44μ insize and the balance consists essentially of particles having a maximumparticle size of 500 to 2000μ, and firing the molded ceramic, and (b) ametal cast around said ceramic part, said ceramic material being aluminaand said cast metal being selected from the group consisting of aluminumalloy and cast iron;wherein, said casting is in the form of a pipe.
 8. Amethod of making a vibration-resistant heat-insulating casting whichcomprises the steps of molding particles of ceramic material having acumulative particle size distribution within the shaded area indicatedin FIG. 4 of the drawings as filed, firing the molded ceramic, and thencasting a metal around the resulting ceramic part, said ceramic materialbeing selected from the group consisting of alumina, cordierite,zirconia and glass ceramic and said casting metal being selected fromaluminum alloy and cast iron.
 9. The method of claim 8, wherein saidceramic particles are compounded with a minor portion of resin prior tomolding.
 10. The method of claim 8, wherein said ceramic material isalumina and said molded ceramic is fired at a temperature of 1350° C. to1750° C.
 11. The method of claim 8, wherein said ceramic material iscordierite and said molded ceramic is fired at a temperature of 1150° C.to 1350° C.
 12. The method of claim 8, wherein said particles of ceramicmaterial are molded into the form of a pipe.
 13. A method of making avibration-resistant heat-insulating casting which comprises the steps ofmolding particles of ceramic material having a cumulative particle sizedistribution such that 14.5-50% of the particles are less than 44μ insize while the balance consists essentially of particles having amaximum particle size ranging between 500 and 2000μ, firing the moldedceramic, and then casting a metal around the resulting ceramic part,said ceramic material being one selected from the group consisting ofalumina, cordierite, zirconia and glass ceramic and said casting metalbeing selected from aluminum alloy and cast iron.
 14. The method ofclaim 13, wherein said ceramic particles are compounded with a minorportion of resin prior to molding.